Soft polyvinyl chloride (PVC) is widely used to produce articles like toys, footwear, profiles, instrument panel skins, furniture, sporting goods and the like. Interest exists in replacing the soft PVC in these applications with materials that are considered more environmentally friendly. Especially with respect to toys for small children, interest exists for substitutes for soft PVC that do not contain components, e.g., phthalate-based plasticizers, which leach or otherwise migrate from the article under normal use conditions. Further, interest exists for these substitutes for soft PVC to be paintable with a primer (e.g., to be implemented in a pre-existing manufacturing process that uses primer) and without requiring another surface treatment, while still imparting the desired Shore A hardness to the resultant article.
Polyolefin substrates such as polypropylene substrates have been proposed. However, due to low surface energy and lack of functional groups (polarity) applying a surface coating (painting layer) to polyolefin substrates is challenging task and this drawback has resulted in limited adoption of polyolefin elastomers in paintable toys. Improvement of the paintability of polymeric substrate is often accomplished through the use of surface pretreatment such as plasma, flaming, corona treatment, ion or electron beam treatment, chemical etching, and solvent degreasing. However, such surface pre-treatments provided disadvantages. For example, solvent degreasing may not result in sufficient adhesion. Also, bulk grafting or compounding with polar ingredients such as polyurethane can effectively enhance the adhesion properties of the thermoplastic polyolefin (TPO) surface, grafting technologies create an additional cost. Further, plasma treatment creates a temporary increase in the surface treatment, but is not very effective for three dimensional articles. Accordingly, it would be desirable to produce a TPO compound with excellent adhesion to paint with primers, without the need for surface treatments or the use of polar components.